Earlier quoted context omitted.
You’re only surprised because you haven’t spent enough time watching pigeons. They’re beautiful birds, many past societies literally worshipped them, and they saved a lot of butts in both World Wars. They’ve fallen from grace because 20th century plus humans don’t like what survives and thrives wild in their cities, especially when they associate them with dirt and garbage the humans leave everywhere .
I've spent plenty of time around pigeons. They've nested a few times within 20 of feet of my apartment. If I don't use adequate protective equipment while cleaning the pigeon shit from my patio, I can be infected with an organism in the shit, namely, Histoplasma capsulatum, Cryptococcus neoformans, Aspergillus fumigatus, Chlamydophila psittaci, Salmonella bacteria, Escherichia coli, Mycobacterium avium complex, Liste…
Oh, and several of those you can’t get at all from a pigeon’s poop, they require an intervening, blood-feeding arthropod.